1. Field of the Invention
The present invention relates to the treatment of prostate cancer, and in particular, relates to a method for treating prostate cancer or reducing the radio-resistance of prostate cancer cells in a subject, wherein the method comprises administering to a subject in need an effective amount of a medicament comprising an active component. The active component is a nanoparticle of a carrier encapsulated with cytolethal distending toxin subunit B (CdtB). The medicament could be used in combination with radiation therapy to provide an outstanding effect on treating prostate cancer.
2. Description of the Related Art
The prostate is a male-specific genital organ. Prostate cancer has become one of the most common cancers in the male population worldwide. The occurrence of prostate cancer is related to age. Along with changes in eating habits, increase in high fatty food intake and increase in average lifespan, the occurrence and mortality of prostate cancer has risen to become one of the top ten most common causes of death from cancer. While the pathology of prostate is unclear, known etiologies include genetics, diet, hormonal and environmental factors. There are usually no symptoms in the early stage of prostate cancer; however, as the tumor invades or blocks the urinary tract or urethral neck, symptoms similar to urinary track blocking occurs. In the advanced stage, symptoms of acute retention of urine, hematuria and aconuresis may appear. In addition, when bone metasis occurs, patients may suffer from symptoms of bone pain, pathological cataclasis, anemia, and paraplegia caused by the compression of the spinal cord.
The common methods for treating prostate cancer include surgery, hormone therapy and radiation therapy. For patients with lymphatic metastasis or bone metastasis, prostate cancer can not be treated effectively because it is difficult to excise all of the metastatic cancer cells with surgery. In addition, surgery is not always recommended for older patients since the postoperative recover time is slower. Because prostate cancer cells in the early stage are androgen-dependent, androgen stimulation is necessary for the growth and division of prostate cancer cells. In the absence of androgen, prostate cancer cells will regress. Therefore, hormone therapies, such as androgen suppression or androgen ablation, are used in clinics to treat prostate cancer. However, because some prostate cancer cells will change into an androgen-independent form after a period of time, such prostate cancer cells can continuously grow despite treatment with androgen suppression or androgen ablation therapy. Therefore, hormone therapy cannot effectively treat prostate cancer.
In view of the above, both surgery and hormone therapy require an additional therapeutic method, such as radiation therapy. Radiation therapy refers to using a focused radiation beam to damage the DNA structure of prostate cancer cells to stop the growth of cells. Another advantage of radiation therapy is that it can be used to treat patients of any age or health status. The dosage and radiating range can become more precise with the use of an apparatus. However, because prostate cancer cells with radio-resistance will generate and cells can grow continuously even under radiation exposure, radiation therapy is less effective in the late stages of treatment.
In view of the limited therapeutic effect of current treatments for prostate cancer, it is important to provide one method or medicament to effectively treat prostate cancer, especially to reduce the radio-resistance of prostate cancer cells and elevate the cure rate of prostate cancer.
The inventors of the present invention found that a nanoparticle of a carrier encapsulated with cytolethal distending toxin subunit B (CdtB) can increase the radiation sensitivity of the prostate cancer cells with radio-resistance so as to reduce the radio-resistance of said prostate cancer cells. Radiation therapy can be used in combination with a carrier encapsulated with cytolethal distending toxin subunit B to provide an increased therapeutic efficacy and reduce the recurrence of prostate cancer in patients. Such treatment option would benefit the elderly or patients who are not suitable for surgery.